If during the first download, they registered your IP, MAC number, or computer serial number it might be NOT possible. But when it didn't happen give it a try anyway.
Otherwise use a different computer. But make sure you first make a complete clean up of what you have downloaded. They might have put a mark in one of your files too.
There are many different ways to detect that you "visit" again.
Some years ago, BNR had no problem downloading their software (Austria)
If you are not violating any copyright on the PLC software demo, the PLC software designer would be your best source to find the workaround. Of course your situation may be that you have used up your 'free' trial, and it is time to buy if you like and want to use more.